Specifying Velocity of Motion in Inverse Kinematics and Inverse Dynamics without Additional Motion Data

[Deepak Singh]

Hello Everyone,

I would like to know about the availability of any feature or method in Opensim 4.0 through which I could specify and modify the velocity of the motion in Inverse kinematics and Inverse dynamics tools without collecting any additional marker and motion data.
I am using Gait2392 model and I am using the sample data files provided with it. But I would like to identify, specify and modify the velocity of the walking motion of the model and observe it's effect on the outputs of inverse kinematics and inverse dynamics.
I know that this can be done in forward dynamics but I would like to know about any possibility to performing the function that I seek.

Please reply as soon as possible.

Regards,
Deepak Singh
Email id: dgaira2@gmail.com

[Carmichael Ong]

You may want to look at the documentation for IK (https://simtk-confluence.stanford.edu/d ... tics+Works) and ID (https://simtk-confluence.stanford.edu/d ... mics+Works) for more info on how they work. IK does a frame by frame optimization to solve for joint positions at each time step, and ID differentiates the joint positions to calculate the joint velocities and accelerations.

In theory you could slow this down or speed this up by changing the time column, however, this does not correctly represent what humans do when the slow down or speed up, and furthermore, could make the simulation dynamically inconsistent with any other data (e.g., external forces). I would not recommend doing this or trusting the results from this procedure.